G. Fishwick

Influence of supplementation with dietary soyabean meal on resistance to haemonchosis in Hampshire Down lambs

The influence of dietary protein supplementation on resistance to haemonchosis was examined in Hampshire down lambs fed either a basal diet or a diet supplemented with soyabean. At seven months of age the lambs were challenged with an initial loading dose of Haemonchus contortus, followed by a trickle infection three times a week. Blood and faecal samples were collected three times a week and bodyweights were recorded weekly. After 10 weeks the lambs were slaughtered and their worm burdens and carcase composition determined. Although their mean worm burdens were similar, the lambs given the basal diet had higher faecal egg counts, lower packed red cell volumes and lower concentrations of total plasma protein and plasma albumin than the lambs given the supplemented diet. The dietary supplementation also improved the carcase composition of the lambs.

Influence of soyabean meal supplementation on the resistance of Scottish Blackface lambs to haemonchosis

Protein supplementation improves the resistance of sheep to haemonchosis. This experiment investigated the Scottish blackface breed to establish whether dietary protein supplementation is still beneficial in a genetically resistant breed. Lambs were given either a basal diet or a diet supplemented with soyabean meal to give an additional 80 g crude protein kg dry matter-1. The lambs were given an initial loading dose of Haemonchus contortus, followed by a trickle infection for 10 weeks. The weight gains of the lambs given the supplemented diet were greater and their carcases were leaner, irrespective of infection status. Infected animals on the basal diet were more anaemic and hypoalbuminaemic than animals receiving the supplemented diet, although there were no statistically significant differences in mean worm burdens or faecal egg counts.

The pathophysiology of Trypanosoma congolense infection in Scottish Blackface sheep. Influence of dietary protein.

The intensity of parasitaemia, degree of anaemia, blood biochemical changes and live weight gains were measured in two groups of Scottish Blackface sheep infected experimentally with bloodstream forms of Trypanosoma congolense and given either a high or a low protein diet. It was observed that infected animals on a high protein diet tended to develop a higher intensity of parasitaemia than those on a low protein diet. Both groups of infected sheep exhibited similar degrees of anaemia, but the erythropoietic activity, as judged by the increase in mean corpuscular volume and appearance of normoblasts in the circulation, was significantly greater in animals on a high protein diet. The infected animals on a high protein diet gained weight at a similar rate to their uninfected controls, while those on a low protein diet gained significantly less than their controls between 0 and 70 days after infection. Following treatment with the trypanocidal drug isometamidium chloride, both infected groups recovered from the anaemia. However, the rate of recovery was faster in animals on a high protein diet than in those on a low protein diet. It was concluded that high protein intake ameliorates the adverse effects arising from infection, as assessed by the severity of anaemia and weight changes, and also enhances the rate of recovery following chemotherapy.

The influence of energy intake on the pathophysiology of Trypanosoma congolense infection in Scottish Blackface sheep

The intensity of parasitaemia, degree of anaemia, live body weight gains and blood biochemical changes were measured in two groups of Scottish Blackface sheep infected experimentally with Trypanosoma congolense and allowed either a high (9.9 MJ metabolisable energy (ME) day-1) or a low (6.1 MJ ME day-1) energy intake. It was observed that infected animals on the low energy intake had a longer mean prepatent period, but following patency they developed more severe anaemia and greater growth retardation than those on the high energy intake. Both infected groups exhibited significant reductions in serum total lipids, phospholipids, plasma cholesterol and albumin. However, these changes were more severe in the animals on the low energy intake than in those on the high energy intake. It was concluded that adequate energy nutrition enhances the ability of infected animals to withstand the adverse effects of infection, by promoting body weight gains and moderating the severity of the pathophysiological changes associated with ovine trypanosomosis.

The influence of relative resistance and urea-supplementation on deliberate infection with Teladorsagia circumcincta during winter.

The consequences for lambs of infection over the winter with Teladorsagia circumcincta were quantified by deliberate, trickle infection of selected animals at 7 months of age. Infected and control uninfected animals were each allocated into four groups, relatively resistant animals on a normal diet, relatively resistant animals on an isocaloric diet supplemented with urea, and relatively susceptible animals on the same two diets. Resistance and susceptibility was assessed by faecal egg counts following natural infection during the summer preceding the deliberate infection. During the deliberate infection egg counts remained low and most parasites recovered at necropsy were inhibited larvae. Nonetheless, infection reduced weight gain, decreased albumin and fructosamine concentrations and provoked a noticeable pepsinogen and eosinophil response. As most larvae were inhibited these responses may have been largely a consequence of immuno-inflammatory responses in the host rather than the direct action of parasites themselves. Relatively resistant animals on the supplemented diet allowed fewer larvae to establish and had higher fructosamine concentrations, higher albumin concentrations and decreased pepsinogen responses. Therefore, a combination of relatively resistant sheep and nutritional supplementation appears most efficient at controlling infection.

The influence of dietary supplementation with urea on resilience and resistance to infection with Haemonchus contortus

Previous research has indicated that supplementing an apparently adequate diet with additional protein improves both host resistance and resilience in lambs infected with Haemonchus contortus. The present study tested the influence of supplementation with non-protein nitrogen (urea). Helminth-naive Hampshire Down lambs were given an apparently adequate basal diet or a diet supplemented with urea. The lambs were then infected with Haemonchus contortus for 10 weeks. Supplementation with urea had no discernible effect on resistance to infection; faecal egg counts, worm burdens, worm lengths and mean number of eggs per adult female worm did not differ between the 2 groups. However, lambs on the supplemented diet showed better resilience; they had greater packed red cell volumes, higher plasma albumin concentrations and increased liveweight gain compared to lambs on the basal diet. The loss of appetite following infection was less in lambs fed the urea-supplemented diet. The observed effect of urea supplementation was seemingly due to greater food consumption as well as the better diet.

Pathophysiology of the periparturient egg rise in sheep: a possible role for IgA

The relationship between anti-parasite IgA antibody levels in plasma and the periparturient egg rise in sheep was investigated. Ostertagia circumcincta larvae (5000 third stage larvae three times weekly) were administered to three groups of seven adult immune ewes from 12 weeks before until three weeks after lambing (group 1) or from six (group 2) or 14 (group 3) weeks before until three weeks before lambing. Seven additional ewes were not challenged (group 4 controls). Ewes in groups 1, 2 and 4 received anthelmintics 14 weeks before lambing. Challenge of the pregnant ewes with O circumcincta larvae resulted in substantial increases in faecal egg counts only during the periparturient period regardless of the larval dosing regimen. Furthermore, the periparturient rise in faecal egg counts was closely associated with a significant increase in anti-parasite IgA antibody levels in plasma. This rise in IgA antibody levels occurred at a time when IgA is transported from the gut to milk during early lactation. It is postulated that this may lead to a temporary reduction in abomasal antibody levels of ewes and hence permit the establishment of larvae and, or, the emergence and development of inhibited larvae and thereby lead to the periparturient rise in faecal egg count.

The patho-physiology of Trypanosoma congolense in Scottish Blackface sheep: influence of diet on digestive function.

The influence of types of roughage, barley straw (diet B) versus lucerne hay (diet U, on the patho-physiology of a T. congolense infection was compared in eight pairs of Scottish Blackface male twin Iambs. One animal of each twin pair was infected and the other used as a pair1ed control. Voluntary food intake, body weight, digestive function, various blood haematological and biochemical measurements were made. Voluntary organic matter intake decreased significantly after the T. congolense infection, the decrease being greater in the diet L group than in the diet B group lambs (P < 0.01). The apparent digestibility coefficients of crude protein and organic matter were significantly lower in the infected lambs (P < 0.01). Mean retention time of the roughage through the digestive tract in the animals given barley straw was significantly longer (P < 0.05) due to a 10UIer rumen outflow rate constant (P < 0.01). Infection resulted in longer mean retention times (P < 0.01). Packed cell volume (PCV) was significantly lower before infection in the animals given diet B (P < 0.01). After infection, diet (P < 0.01) and infection (P < 0.01) had an additive effect on PCV. The anaemia was both macrocytic (P < 0.05) and hypochromic (P < 0.01). Diet B resulted in higher plasma cholesterol (P < 0.05), but lower plasma urea (P < 0.01) and albumin (P < 0.01) concentrations before infection than diet L. The T. congolense infection significantly lowered plasma cholesterol (P < 0.01) and increased plasma urea (P < 0.01) concentrations compared with the uninfected controls. Plasma albumin concentrations decreased, but were more affected by nutrition (P < 0.01) than by infection (P < 0.05). It was concluded that the patho-physiological effects of the T. congolense infection in the Scottish Blackface Iambs were affected by the type of roughage offered, but that these effects were additive rather than interactive to the effects of infection.